1. Field of the Invention
The present invention relates to a magnetic-disk evaluation apparatus (i.e., a spin stand) for determining, without writing actual servo signals to a magnetic disk, whether temporary servo signals previously written to a magnetic disk by magnetic transfer are acceptable. The present also further relates to a method for evaluating temporary servo signals previously written to a magnetic disk for use in the self servo writing method for magnetic disk apparatuses.
2. Description of the Related Art
Hard disk drives (HDD) are commonly used as information storage devices, and operate to position their heads on the basis of servo signals written to a magnetic disk.
Referring now to FIG. 1, a conventional HDD 30 [hereinafter HDD 30] includes a magnetic disk 1 rotatable at several thousand rpm by a spindle motor 2. During rotation, air flow above magnetic disk 1 causes a slider 4 located at the tip of a rotary positioner 3 to float slightly above magnetic disk 1.
A magnetic head 5 is located at an end of slider 4. During operation, servo signals are magnetically written on magnetic disk 1 and are detected by magnetic head 5, amplified by a preamplifier 6, and demodulated by a servo demodulating circuit 7, to obtain track information (indicating on which track the magnet head is lying) and a PES (Position Error Signal, which indicates how far the head is separated from the center of a track).
During operation, HDD 30 determines the current head position by using magnetic head 5 to read the servo signals, and positions magnetic head 5 on a track (target track) with desired information written thereto by using a voice coil motor (VCM) 8 to drive rotary positioner 3.
That is, the difference between the target track position and the head position is detected as the PES, which is input to a compensator 9. Then, compensator 9 generates a drive command to rotary positioner 3 on the basis of the PES and transmits this drive command to voice coil motor (VCM) 8 through power amplifier 10. In this manner, voice coil motor (VCM) 8 drives rotary positioner 3. Thus, feeding back the PES serves to reduce the positional difference between the target track and the head position. Further, in terms of absolute coordinates, the target track position varies in accordance with rotational cycles due to the eccentricity of the disk itself.
During operation, magnetic disk 1 has the above servo signals and data recorded thereon and reproduced therefrom by magnetic head 5. A defect in magnetic disk 1 prevents proper recording or reproduction. Thus, magnetic disk 1 must be tested before integration (that is, magnetic disk 1 is clamped to spindle motor 2) to ascertain that magnetic disk 1 can provide minimum required performance.
The test consists of using a magnetic head to sequentially check magnetic disk 1 for its gliding property, its certify property, and its contact start stop (CSS) property. The gliding property check consists of checking the number of projections on magnetic disk 1. The certify property check consists of checking magnetic disk 1 for its electric properties and defects. The contact start stip (CSS) property check consists of checking the durability of magnetic disk 1.
It should be understood, that an apparatus used to evaluate the performance of magnetic disk is called a xe2x80x9cspin stand.xe2x80x9d
Referring additionally now to FIG. 2 shows a xe2x80x9cspin standxe2x80x9d having a base 11 which supports a spindle motor 12. During operation, spindle motor 12 rotates at an arbitrary rotation speed allowing magnetic disk 1 to be evaluated. An evaluating magnetic head 13 reproduces and records signals on and from magnetic disk 1 in order to evaluate magnetic disk 1. A carriage 14 supports evaluating magnetic head 13. A xe2x80x98xcex8xe2x80x99 stage 15 [hereinafter xcex8 stage 15] adjusts carriage 14 to an arbitrary angle. A stage 16 is movable in at least one direction along a guide 17 in order to freely vary the positional relation ship between spindle motor 12 and evaluating magnetic head 13. It is to be understood, that stage 16 is movable in a direction in FIG. 2 along guide 17.
It is to be understood, that HDD 30, based on the head positioning method using rotary positioner 3 driven by voice coil motor (VCM) 8, has the advantage of having a compact structure but also has a drawback in that the head skew angle varies with the track.
The head skew angle relates to the flying head height of magnetic head 13 and causes variations in the reproduction output from magnetic head 13. Accordingly, the same skew angle as that in conventional HDD 30 must also be used in conducting the above-described gliding, certifying, and CSS property checks in order to evaluate the performance of magnetic disk 1.
Thus, for these checks, the positional relationship between spindle motor 12 and evaluating magnetic head 13 of the spindle stand must be adjusted to be identical to that in HDD 30, so that commonly used spin stands must include a positioning mechanism based upon directly moving stage 16, the rotary xcex8 stage 15, or similar parts.
The above-described checks are then carried out using the spin stand and, if magnetic disk 1 is determined to be acceptable, magnetic disk 1 is clamped to spindle motor 2, which is then assembled into HDD 30.
With magnetic disk 1 integrated into HDD 30 (that is, magnetic disk 1 is clamped to spindle motor 2), a device called a xe2x80x9cservo track writer (STW) xe2x80x9d is used to write servo signals to magnetic disk 1.
Additionally referring now to FIG. 3, during operation, the servo track writer (STW) is used to produce servo tracks. During operation, the servo track writer (STW) conventionally presses a pin 19, accurately positioned by an external actuator 18, against rotary positioner 3 inside HDD 30, via a link 20 for positioning, while setting the head position on the basis of a scale inside actuator 18 using a fine feeding mechanism.
Since the servo signals are each written to a corresponding one of the tracks on magnetic disk 1, the servo track writer (STW) must write the servo signals to all the tracks on magnetic disk 1 while executing accurate positioning via link 20. Since an increase in recording density increases the number of tracks while reducing the track width, the servo track writer (STW) must execute more accurate positioning on a larger number of tracks.
Unfortunately, this realization of accurate positioning requires a rigid and expensive mechanical positioning mechanism as well as a large amount of time for writes. Consequently, multiple servo track writers (STW) must be provided for parallel processing, further requiring a larger space in manufacturing clean rooms in which the servo track writers (STWs) are arranged. This requirement also increases costs.
Considerable effort has been put into developing a method for omitting the above described servo track writers (STWs) and causing HDD 30 to execute self servo writing.
Additionally referring now to FIG. 4, temporary servo signals 21 have already been written to magnetic disk 1. It is to be understood, that temporary servo signals 21 can be written to magnetic disk 1 substantially faster than with the servo track writers (STWs). This faster writing may be accomplished, for example, by using a technique such as magnetic printing to copy a magnetic pattern from a master disk (not shown).
After an initial writing, magnetic disk 1 is integrated into HDD 30, which then writes only actual servo signals 22 to disk 1 on the basis of temporary servo signals 21.
Subsequently, the magnetic head is positioned on the basis of actual servo signals 22, and it is confirmed that HDD 30 operates correctly.
Unfortunately, if HDD 30 cannot operate correctly due to any defect in either actual servo signals 22 or temporary servo signals 21, the positioner section must be disassembled so that magnetic disk 1 can be replaced with a new one, to which temporary servo signals 21 and actual servo signals 22 are then rewritten.
Additionally referring now to FIG. 5, the servo signals are stored on the unitary magnetic disk, so that when magnetic disk 1 is chucked on spindle motor 12 of the spin stand, the central position of tracks 21 formed from recorded servo signals may be offset from the central position of spindle motor 12 by several ten to thousand micrometers.
Consequently, signals reproduced from tracks 21 are observed to be eccentric to the rotational center of magnetic disk. A maximum size A, is defined as a maximum eccentricity of tracks 21. Thus, following up servo signals requires the formation of a control system that compensates for this eccentricity.
Unfortunately, although the object of the conventional method is to reduce the amount of time required by the servo track writers (STWs), and to reduce costs, the quality of the servo signals cannot be evaluated before writing actual servo signals 22 to magnetic disk 1. Consequently, this method requires the same operation to be performed twice and is thus inefficient in terms of costs and time.
Thus, if servo signals have already been recorded on the unitary magnetic disk, evaluation of the unitary magnetic disk is conducted, and before magnetic head 5 is integrated into HDD 30, it must be furthermore determined on the basis of temporary servo signals 21, previously recorded on magnetic disk 1, that actual servo signals 22 can be used in order to evaluate the unitary magnetic disk and to position magnetic head 5.
It is an object of the present invention to overcome the detrimental concerns described above.
It is another object of the present invention to provide a magnetic-disk evaluating apparatus and a method that can determine whether temporary servo signals are acceptable without writing the actual servo signals to the magnetic disk.
It is another object of the present invention to provide an apparatus where even if the magnetic head is moved to various positions, the measuring instrument moves correspondingly and thus need not be adjusted, facilitating measurement of the positional displacement of the magnetic head.
Briefly stated, the present invention provides a magnetic-disk evaluation apparatus including a magnetic head positioned on the basis of temporary servo signals. Fluctuation of the magnetic head in a seek direction is measured using a measurement device. A measuring rotating arm moves in tandem with a rotating stage holding a rotary positioner. The measurement device is installed on the measuring rotating arm. The rotary positioner is controlled on the basis of the temporary servo signals to position the magnetic head on a circle, concentric from a center of a spindle motor operating a magnetic disk. Fluctuation of the magnetic head in the seek direction is measured to detect the displacement of a tip of the magnetic head and to determine whether the temporary servo signals are acceptable based upon the displacement.
According to an embodiment of the present invention there is provided a magnetic-disk evaluation apparatus, for evaluating a magnetic disk having a plurality of temporary servo signals, comprising: a spindle motor, the spindle motor operating the magnetic disk at a rotation speed effective to enable an evaluation of the magnetic disk, a rotary positioner supporting a magnetic head about a rotation shaft, the magnetic head operable relative to the spindle motor and the magnetic disk, control means for controlling the rotary positioner and the magnetic head on a basis of the plurality of temporary servo signals and positioning the magnetic head relative to a concentric circle centered on the spindle motor prior to the evaluation of the plurality of temporary servo signals, measurement means for accurately measuring a head displacement of the magnetic head in a seek direction relative the magnetic disk, detection means for detecting a tip displacement of a tip of the magnetic head on a basis of the head displacement in the seek direction, and determination means for determining whether the temporary servo signals are acceptable, on a basis of the tip displacement, effective to allow the magnetic-disk evaluation apparatus to effective and rapidly evaluate the magnetic disk.
According to an embodiment of the present invention there is provided a magnetic-disk evaluation apparatus, for evaluating a magnetic disk having a plurality of temporary servo signals, further comprising: fixation means for temporary fixing the rotary positioner effective to locate the magnetic head at an arbitrary position on the magnetic disk, a positioner rotating stage for supporting the fixation means and the rotary positioner and moving the rotary positioner, fixed by the fixation means, to an arbitrary position on the magnetic disk, the positioner rotating stage rotating around a rotating center, a measuring rotating arm rotating around the same the rotating center as the positioner rotating stage based on a movement angle of the positioner rotating stage, and the measurement means on the measuring rotating arm, whereby the measurement means is positioned to effectively measure the displacement of the magnetic head in the seek direction.
According to an embodiment of the present invention there is provided a magnetic-disk evaluation apparatus, for evaluating a magnetic disk having a plurality of temporary servo signals, wherein the control means further comprises: storage means for storing an eccentricity of the magnetic disc measured on a basis of a first signal from the magnetic head reading the temporary servo signals while the rotary positioner is fixed by the fixation means, cancel means for canceling the eccentricity of the magnetic disk in the first signal from the magnetic head by receiving a feed forward input of the eccentricity stored in the storage means and by generating a second signal, and feedback compensating means for generating, from at least the second signal sent from the cancel means, a third signal for feedback-controlling of the rotary positioner, enabling effective cancellation of eccentricity in a speedy manner.
According to an embodiment of the present invention there is provided a magnetic-disk evaluation apparatus, for evaluating a magnetic disk having a plurality of temporary servo signals, wherein: the measurement means is a laser Doppler vibrometer effective to measure the displacement of the magnetic head in the seek direction by irradiating a side of the magnetic head with a plurality of laser beams and receiving a reflection therefrom.
According to another embodiment of the present invention there is provided a magnetic-disk evaluation apparatus, for evaluating a magnetic disk having a plurality of temporary servo signals, comprising: a spindle motor, the spindle motor operating the magnetic disk at a rotation speed effective to enabling an evaluation of the magnetic disk, a rotary positioner supporting a magnetic head about a rotation shaft, the magnetic head operable relative to the spindle motor and the magnetic disk, control means for controlling the rotary positioner and the magnetic head on a basis of the plurality of temporary servo signals and positioning the magnetic head relative to a concentric circle centered on a center of the spindle motor prior to the evaluation of the plurality of temporary servo signals, measurement means for accurately measuring a head displacement of the magnetic head in a seek direction, detection means for detecting a tip displacement of a tip of the magnetic head on a basis of the head displacement in the seek direction, determination means for determining whether the temporary servo signals are acceptable, on a basis of the tip displacement, effective to allow the magnetic-disk evaluation apparatus to effective and rapidly evaluate the magnetic disk, fixation means for temporary fixing the rotary positioner effective to locate the magnetic head at an arbitrary position on the magnetic disk, a positioner rotating stage for supporting the fixation means and the rotary positioner and moving the rotary positioner, fixed by the fixation means, to an arbitrary position on the magnetic disk, the positioner rotating stage rotating around a rotating center, a measuring rotating arm rotating around the same the rotating center as the positioner rotating stage based on a movement angle of the positioner rotating stage, and the measurement means on the measuring rotating arm, whereby the measurement means is positioned to effectively measure the displacement of the magnetic head in the seek direction.
According to an embodiment of the present invention there is provided a magnetic-disk evaluation apparatus, comprising: a magnetic disk including a plurality of temporary servo signals, a spindle motor on the magnetic-disk evaluation apparatus, the spindle motor effective to enable an evaluation of the magnetic disk, a magnetic head operable relative to the spindle motor and the magnetic disk, a rotary positioner supporting the magnetic head about a rotation shaft, the rotation shaft supporting at least the magnetic head and the rotary positioner, voice coil means at a first end of the rotary positioner opposite the magnetic head effective to drive the rotary positioner on a basis of a command, control means for issuing the command and controlling the rotary positioner on a basis of the plurality of temporary servo signals and positioning the magnetic head relative to a concentric circle centered on a center of the spindle motor prior to the evaluation of the plurality of temporary servo signals, measurement means for accurately measuring a first displacement of the magnetic head in a seek direction, detection means for detecting a second displacement of a tip of the magnetic head on a basis of the first displacement in the seek direction, and determination means for determining whether the temporary servo signals are acceptable, on a basis of the second displacement, effective to allow the magnetic disk evaluation apparatus to effective and rapidly evaluate the magnetic disk.
According to another embodiment of the present embodiment there is provided a magnetic-disk evaluation apparatus for evaluating a magnetic disk, comprising: a base effective to support the magnetic-disk evaluation apparatus, a spindle motor on the base, the spindle motor rotatable at an arbitrary rotation speed effective to enable the evaluation of the magnetic disk, a magnetic head operable relative to the spindle motor, the magnetic head effective for recording electronic signals on and for reproducing electronic signals from the magnetic disk to enable the evaluation, a suspension supporting the magnetic head, a rotary positioner supporting the suspension about a rotation shaft, a voice coil at a first end of the rotary positioner opposite the magnetic head, the rotation shaft cantilevered from the base and supporting the magnetic head, the suspension, and the rotary positioner, a first and a second magnet opposite a respective first and second side of the voice coil, the magnetic disk including a plurality of temporary servo signals, control means for control driving of the rotary positioner on a basis of the plurality of temporary servo signals and being effective to position the magnetic head on a circle concentric to a center of the spindle motor, prior to an initial evaluation of the plurality of temporary servo signals, measurement means for measuring a head displacement of the magnetic head in a seek direction, detection means for detecting a tip displacement of a tip of the magnetic head on a basis of the head displacement in the seek direction, and determination means for determining whether the temporary servo signals are acceptable, on a basis of the tip displacement, whereby the magnetic-disk evaluation apparatus can rapidly and effectively evaluate the magnetic disk.
According to another embodiment of the present invention there is provided a magnetic-disk evaluation apparatus, further comprising: fixation means for temporarily fixing the rotary positioner effective to locate the magnetic head at an arbitrary position on the magnetic disk, a positioner rotating stage for supporting the fixation means and the rotary positioner and moving the rotary positioner, fixed by the fixation means, to an arbitrary position on the magnetic disk, the positioner rotating stage rotating around a rotating center, and a measuring rotating arm rotating around the same the rotating center as the positioner rotating stage based on a movement angle of the positioner rotating stage, and the measurement means on the measuring rotating arm, whereby the measurement means is positioned to effectively measure the displacement of the magnetic head in the seek direction.
According to another embodiment of the present invention there is provided a magnetic-disk evaluation apparatus, wherein: the measurement means is a laser Doppler vibrometer effective to measure the displacement of the magnetic head in the seek direction by irradiating a side of the magnetic head with a plurality of laser beams to receive a reflection therefrom.
According to another embodiment of the present invention there is provided a magnetic-disk evaluation apparatus, wherein the control means further comprises: storage means for storing an eccentricity of the magnetic disc measured on a basis of a first signal from the magnetic head reading the temporary servo signals while the rotary positioner is fixed by the fixation means, cancel means for canceling the eccentricity of the magnetic disk in the first signal from the magnetic head by receiving a feed forward input of the eccentricity stored in the storage means and by generating a second signal, and feedback compensating means for generating a third signal for feedback-controlling of the rotary positioner, from the second signal sent from the cancel means whereby the eccentricity is effectively canceled in a speedy manner.
According to another embodiment of the present invention there is provided a magnetic-disk evaluation method for evaluating a magnetic disk, employing a magnetic-disk evaluation apparatus having a base as a support for the apparatus, a spindle motor on the base for rotating the magnetic disk at an arbitrary rotation speed, a magnetic head for recording and reproducing signals on and from the magnetic disk effective to evaluate the magnetic disk, a suspension supporting the magnetic head, a rotary positioner supporting the suspension, a voice means at first end of the rotary positioner opposite to the magnetic head, a rotating shaft cantilevered from the base, the rotating shaft supporting the magnetic head, the suspension, and the rotary positioner, comprising: a control step of operative control driving of the rotary positioner on a basis of a plurality of temporary servo signals and position the magnetic head on a concentric circle in a center of the spindle motor, before evaluating performance of the temporary servo signals previously written to the magnetic disk, a measurement step of measuring a displacement of the magnetic head in a seek direction, a detection step of detecting displacement of a tip of the magnetic head on a basis of the displacement in the seek direction measured by a measurement means for measuring the displacement, and a determination step of determining whether the temporary servo signals are acceptable, on the basis of the displacement detected by the detection means, whereby a disk evaluation is made speedier and more effective.
According to another embodiment of the present invention there is provided a magnetic-disk evaluation method, wherein the measurement step further includes a step of detecting the displacement of the magnetic head by irradiating a side of the magnetic head with a plurality of laser beams to receive reflected light therefrom, whereby accuracy of the measurement step is increased.
According to another embodiment of the present embodiment there is provided a magnetic-disk evaluation method, wherein the control step further comprises: a storage step of storing the eccentricity of the magnetic disc measured on the basis of the signal from the magnetic head reading the temporary servo signals while the rotary positioner is fixed, a cancel step of canceling the eccentricity of the magnetic disk in the signal from the magnetic head by receiving a feed forward input of the eccentricity stored in the storage means, and a feedback compensating step of generating a signal for feedback-controlling of the rotary positioner, from the signal having the eccentricity canceled at the cancel step.
The present invention further provides a magnetic-disk evaluation apparatus comprising a base as a support table for the apparatus, a spindle motor provided on the base to rotate, at an arbitrary rotation speed, a magnetic disk to be evaluated, a magnetic head for recording and reproducing signals on and from the magnetic disk to evaluate the magnetic disk, a thin suspension for supporting the magnetic head, a thick rotary positioner for supporting the suspension, a voice coil provided at an end of the rotary positioner located opposite to the magnetic head, a rotating shaft installed to protrude from the base and support the magnetic head, the suspension and a pair of magnets sandwiching the voice coil.
The apparatus further includes a control means operative before evaluating performance of temporary servo signals previously written to the magnetic disk, to control driving of the rotary positioner on the basis of the temporary servo signals so that the magnetic head is positioned on a circle concentric to a center of the spindle motor. The apparatus also includes a measurement means for measuring displacement of the magnetic head in a seek direction, detection means for detecting displacement of the tip of the magnetic head on the basis of the displacement in the seek direction which has been measured by the measurement means, and determination means for determining whether the temporary servo signals are acceptable, on the basis of the displacement detected by the detection means.
According to an embodiment of the present invention, there is provided a magnetic-disk evaluation apparatus comprising fixation means for temporarily fixing the rotary positioner so that the magnetic head is located at an arbitrary position on the magnetic disk, positioner rotating stage for supporting the fixation means and the rotary positioner and moving the rotary positioner, fixed by the fixation means, to an arbitrary position on the magnetic disk, and a measuring rotating arm rotating around the same rotating center as that of the positioner rotating stage and depending on a movement angle of the positioner rotating stage, and in that the measurement means is installed on the measuring rotating arm.
According to another embodiment of the present invention, there is provided a magnetic-disk evaluation apparatus further characterized by the measurement means being a laser Doppler vibrometer for measuring the displacement of the magnetic head in the seek direction by irradiating a side of the magnetic head with laser beams to receive a light reflected.
According to another embodiment of the present invention, there is provided a magnetic-disk evaluating apparatus further characterized in that the control means consists of storage means for storing eccentricity of the magnetic disc measured on the basis of a signal from the magnetic head reading the temporary servo signals while the rotary positioner is fixed by the fixation means, cancel means for canceling the eccentricity of the magnetic disk in the signal from the magnetic head by receiving a feed-forward input of the eccentricity stored in the storage means, and feedback compensating means for generating a signal for feedback-controlling of the rotary positioner, from the signal sent from the cancel means and having the eccentricity canceled.
According to another embodiment of the present embodiment there is provided a magnetic evaluation method in a magnetic-disk evaluating apparatus having the same configuration as that of an actual hard disk drive and comprising a base as a support table for the apparatus, a spindle motor provided on the base to rotate, at an arbitrary rotation speed, the magnetic disk to be evaluated, a magnetic head for recording and reproducing signals on and from the magnetic disk to evaluate the magnetic disk, a thin suspension for supporting the magnetic head, a thick rotary positioner for supporting the suspension, a voice coil provided at an end of the rotary positioner located opposite to the magnetic head, a rotating shaft installed so as to protrude from the base, for supporting the magnetic head, the suspension and the rotary positioner, and a pair of magnets sandwiching the voice coil, the method being characterized by consisting of a control step being operative before evaluating performance of temporary servo signals previously written to the magnetic disk, in order to control driving of the rotary positioner on the basis of the temporary servo signals so that the magnetic head is positioned on a concentric circle in the center of the spindle motor, a measurement step of measuring displacement of the magnetic head in a seek direction, a detection step of detecting displacement of the tip of the magnetic head on the basis of the displacement in the seek direction measured by the measurement step, and a determination step of determining whether the temporary servo signals are acceptable, on the basis of the displacement detected by the detection step.
The above, and other objects, features and advantages of the present invention will become apparent from the following description read in conjunction with the accompanying drawings, in which like reference numerals designate the same elements.